A filter bed or a filtering apparatus which filters to-be filtered water containing turbid materials is provided with filtering material for capturing turbid materials. As the filtering material, there are relatively expensive film and special filter element, but there are also inexpensive filtering materials such as gravels and filtering sands, and they can repeatedly be used if they are washed. The rapid sand filter bed or the slow sand filter bed provided in a water purification plant includes filtering materials such as the gravels and filtering sands. The filtering material of the rapid sand filter bed includes layers of gravels laminated such that particle diameters become smaller upward, and a layer of filtering sands laminated on the layer of gravels and having average particle diameters of 0.45 to 0.7 mm. Flocculating agent is injected into raw water taken from river, lake or a dam, turbid materials are removed in a sedimentation basin to some extent, bactericidal sodium hypochlorite or chlorine is injected and then, the water is filtered downward in the rapid sand filter bed. The filtering material of the slow sand filter bed also includes a layer of gravels laminated such that particle diameters thereof become smaller upward, and a layer of filtering sands laminated on the layer of gravels and having average particle diameters of 0.3 to 0.45 mm. In the slow sand filter bed also, like the rapid sand filter bed, raw water is filtered downward, but a sedimentation basin is not required, and sodium hypochlorite or chlorine is not injected. It is known that a biological film made of microbe is formed in the layer of the filtering sands, organic matters in water are decomposed and delicious purified water can be obtained. An upward-type filtering apparatus which filters raw water upward through filtering materials is also known and is described in a patent document 1 for example. The filtering materials of the upward-type filtering apparatus include layers of gravels laminated such that particle diameters become smaller upward, and a layer of filtering sands laminated on the layer of gravels, and raw water is filtered upward through the filtering material.